Cardiac rhythm management devices have been developed to provide pacing stimulation to one or more heart chambers in an attempt to improve the rhythm and coordination of atrial and/or ventricular contractions. Cardiac rhythm management devices typically include circuitry to sense signals from the heart and a pulse generator for providing electrical stimulation to the heart. Typically, leads extend into the patient's heart chamber and/or into veins of the heart. The leads often include electrodes that sense the heart's electrical signals and deliver electrical stimulation to the heart in accordance with various therapies aimed at improving cardiac function.
Pacing therapy has been used in the treatment of heart failure (HF). Heart failure causes diminished pumping power of the heart, resulting in the inability to deliver sufficient blood to meet the demands of peripheral tissues. Heart failure can cause weakness, loss of breath, and build up of fluids in the lungs and other areas. In some cases, HF can occur when deterioration of the muscles of the heart result in an enlargement of the heart and/or reduced contractility. The reduced contractility tends to decrease the cardiac output of the heart. In some cases, HF can occur when contractions of the left and right heart chambers are not synchronized properly, denoting atrial or ventricular dyssynchrony. Particularly when the left or right ventricles are affected, the unsynchronized contractions can significantly decrease the pumping efficiency and cardiac output of the heart.